The present invention pertains to jet engines and more particularly to jet engines adapted for ground-based applications, such as in industry and education, wherein conventional jet engines have proven wanting.
While it is not a new idea to use jet engines in industry, rarely are the full benefits realized. Because aircraft jet engines are designed to optimize their flight related functions, many of the features emphasized in the design make them unsuited for most other applications. Two serious obstacles to their use in industry are; high initial cost and low application efficiency.
Application efficiency takes into account all the economic factors related to the use to which the engine is put, the effectiveness in doing the work desired and innumerable other considerations. While jet engines are outstanding in reliability when used in aircraft with precise maintenance sheduling, they generally have proven unreliable when operated in an environment for which they were not designed, and when operation and maintenance are by personnel not properly trained. Maintenance costs are much higher than with reciprocating engines.
Aircraft turbojet engines are engineered, for example, with these goals: frontal area is kept minimum, ratio of power output to pounds weight in emphasized, fuel consumption for pound thrust is minimized, self-containment of ancillary drives and components is demanded, reliability and safety must be at maximum. These most rigid requirements result in high cost design. Many of these features may be compromised in designing for ground based operation.
They are almost always too powerful and fuel consumption is excessive. It can be assumed that a simple jet engine, even with a somewhat higher specific fuel consumption, will have a higher application efficiency when designed to the specific industrial use. The poor application efficiency of aircraft jet engines when adapted to industrial use is illustrated by the high operating costs and low reliability of the jet powered snow blowers used by railroads.
In spite of complexity and cost, turbojet engines have been adapted to a limited extent to ground based power generation. For example: where high temperature and high velocity exhaust gas can be used for blowing or moving gasses, thawing, melting and drying; where enormous shaft power is required; and where suitable fuel is plentiful.
As fundamental principals of design and operation of the engine of this invention are the same as used in the design of the more complex airplane turbojet engine, it is inherently more suitable for training engineering students in the fundamentals of turbojet engine design.
The low cost jet engine of the present invention is intended for ground based application and is simply constructed of a conventional automotive turbocharger, which includes a compressor and a turbine, and an independent combustor mounted on the turbocharger between the compressor and the turbine. The combustor is adapted for taking in air from the turbocharger compressor and combusting fuel with the compressed air to provide an exhaust for driving the turbocharger turbine. Appropriate controls are provided for starting and controlling the operation of the engine.
This invention is a turbojet engine which is both simple and low cost with the proven automotive turbocharger as the its core. With its proper design of; combustor, ancillary components and systems, and controls, is inexpensive and highly reliable. Much of its construction is from mass produced components. Also, with its simplicity of design and only one rotating part, repairs are easily accomplished and the mass produced commercial parts are inexpensive. The ability to tailor engine design to specific industrial uses results in an application efficiency not achievable by adaptation of aircraft jet engines.
Reducing the complexity brings with it a loss in specific fuel consumption in comparison to conventional turbojet engines. This efficiency loss is relatively unimportant in applications of supplying emergency power, replacing manual labor, blowing snow, thawing materials, propelling granular materials, training engineering students and many other uses.
The principal components of a typical turbojet aircraft engine are the compressor, turbine, and a fuel combustor. Ancillaries are; lubricating system, fuel management system, staring system, controls and instrumentation.
As aircraft engines must be self-sustaining, these ancillaries are driven by shaft output from the jet engine, through a gearing mechanism. This feature is a major and often unnecessary cost and complication in ground based applications.
Examples of application efficiency in design are important features gained by using outside power to drive the ancillaries. Oil under pressure is supplied at the bearings before a start is attempted; pressure is maintained at the bearings during spinning down after a shutoff. This both assures lubrication after shutoff and cools the bearings and turbocharger housing to prevent coking of oil (forming carbon) which eventually destroys the turbocharger. Also, fuel pressure is available prior to the start attempt.
The forced lubrication system for pumping lubrication oil through the turbocharger is provided with a means for heating the oil at selected times, such as at start-up when the oil is cold. In addition, the lubrication system preferably includes a fuel heat exchanger that is adapted for heating fuel for the combustor with the lubrication oil. The lubrication oil may also be cooled with a heat exchanger that includes a cooling core that is adapted for cooling the lubrication oil flowing through the core. The cooling core is normally positioned at the intake of the turbocharger compressor for cooling the core with compressor intake air.
The oil heat exchanger further preferably includes a thermostatic bypass valve adapted for bypassing flow quantities of lubricating oil around this cooling core when temperature of the lubricating oil attains a predetermined minimum, in order to prevent the lubrication oil from becoming undesirably low.
The fuel supply system for supplying fuel under pressure to the combustor for combustion includes a throttle valve that is adapted for bypassing flow of fuel to the combustor for thereby regulating fuel supply to the combustor. Accordingly, the fuel supply is continuously circulated and when fed to the combustor nozzle, the quantity of fuel through the throttle is regulated by bypassing quantities of the fuel that is being recirculated to the nozzle. The fuel is also preferably heated by the use of a heat exchanger from the lubrication oil. An additional heating element is also provided for initially heating fuel supplied to the combustor during start-up.
An air nozzle adapted for directing compressed air from an independent source into the compressor of the turbocharger is provided for inducing start-up rotation of the turbine. A pressure sensor in the combustor is provided and adapted for discontinuing the flow of air from the nozzle and for discontinuing an externally supported fuel ignitor in the combustor when a predetermined minimum pressure for self-sustaining operation of the engine is attained.
This invention is a low cost turbojet engine manufactured around the automotive type turbocharger. The combustor, turbine and rotating components are of design and construction well known to the industry. The invention is in having designed in solutions to engineering and manufacturing problems for achieving a simple, reliable, low cost engine.
Product developers who attempt to adapt aircraft design jet engines to their needs will find the versatility of this invention to be the solution to their problems. For applications which require high temperature high velocity gas movement as a means of doing work at specific jobs can design their product around this engine.
Designers of jet engines or their components find it extremely costly and inefficient to test their design ideas on giant multi-burner aircraft type engines. My inventions allow these tests to be set up and run quickly and inexpensively, yet yielding the test data necessary for checking the design.
During heavy snow falls, railroads are faced with need for removing snow from track switches to assure their movement as directed. With the many products which are used for this purpose, still the largest number of switches cleared are by hand with broom and shovel. This problem is particularly critical in marshalling yards with thousands of switches to be cleared quickly.
Of many possible embodiments of this invention, the three preferred embodiments descriptions follow: 1) BASIC MULTI-USE JET ENGINE, 2) EDUCATIONAL and EXPERIMENTAL JET ENGINE PACKAGE, and, 3) SNOW BLOWER FOR RAILROADS.